Proper tongue function is important in many oral activities including food transport, deglutition, speech and maintenance of dental relations. Because the tongue lacks a typical system of skeletal support, it is an unusual structure biomechanically. There is as yet no general model on the mechanism by which tongue movements are produced. This proposal will approach this problem by studying tongue morphology, movements and biomechanics in a series of mammals including opossums, cats and macaque monkeys. This work will proceed in four stages: 1) A histological study of the musculature, nervous and vascular tissues and proprioceptive receptors in the tongue. The emphasis will be on tongue musculature, and these muscles will be divided into major biomechanical units. 2) An analysis of cineradiographic data on the specific pattern of tongue movement in mammals. 3) An extenion of preliminary biochemical models of movement in muscular-hydrostats to organs with complex morphology and movements such as mammalian tongues. 4) The testing of these models by electromyographic recordings of muscle activity during normal tongue movements. These four specific aims reflect four types of information: 1) structure, 2) function, 3) hypotheses on the relation of structure to function and 4) tests of these hypotheses by direct experimental methods. These data on the morphological basis of tongue movements will be the first of their type. They will aid in evaluation of tongue function and dysfunction and will serve as an important base for the construction of models on the neural control of tongue movements.